Positive Temperature Coefficient Circuit Protective Devices
The above photo shows a PTC board. It provides protection for 32 SAMs. The board may be supplied with either solder tab connections (shown), wire-wrap terminals, or .100 mass-termination connectors. The boards are designed for SAMs operating from 10 to 20 volts DC with coil resistances in the 20 to 30 ohm range. Power is connected to the blue terminals with a pair of #12 stranded wires from the main power distribution bus (recommended #6 for up to 6 PTC boards). Wiring to the SAMs is recommended as #24 AWG or larger and the wiring paths should be kept as short as possible. The circuit design works with either positive-common or negative-common SAMs.
The above photo shows a typical installation of PTC protection boards being used with a Z-tronics combination action system. It is recommended that the PTC boards shall be mounted where there can be unobstructed air flow to the boards and not over any heat sources. PTCs heat when tripped and require natural air circulation to meet manufacturer's operating requirements. A circuit fault can easily be detected by feeling the PTCs and finding the one(s) that are warm indicating a tripped state. It is recommended that the boards be mounted on stand-offs to permit better air circulation but this is not a requirement. In this installation #6 power distribution buses are placed horizontally just below the PTC boards (red for positive) and driver boards (black for negative). Individual SAM circuit wiring is routed vertically to each PTC/driver board and the individual #24 kynar insulated conductors are cabled and wrapped with fire-resistant electrical tape to meet NEC requirements. The above installation is for a console using 289 Syndyne stop action magnets (SAMs). System operating voltage of 19 volts is supplied by 8 Gates Cyclone 25aH batteries. An Acopian Power Supply serves to maintain battery charge. PTCs are available from several sources including Wickmann, Schurter, Raychem, and Littlefuse. Click on either of the links below for additional technical information on PTCs.
Wickmann PTC Application Note
Wickmann PTC Data Sheet
Design by: Robert E. Wilhelm, Jr.